Timber and Architecture

Timber has always been a favoured material for its warmness and texture. It has been extensively used not only in interiors but also as external cladding.

Many architects and designers as well as owners alike love the material for its unique character. This is the prime reason why it is used in expressions ranging from tropical and zen simplicity to modernist articulations and variations. In Singapore architecture, there is also a lot of interest in its applications.

Let's look at 2 popular types of timber used as external cladding in Singapore architecture - balua and chengai. The characteristics of each vary but essentially balau is more rugged while chengai is more delicate.

Typically the properties of balau timber vs chengai timber are:

Balau Timber

1. Harder (than chengai timber) - Therefore less cracks when exposed under sun.

2. Less 'pin-holes' - The walnut like grooves typical of natural timber

3. Darker colour

4. Cost - Typical cost is $73/ ft2

Chennai Timber
1. Softer, but more stable - There are more cracks when exposed to sun.
2. More 'pin-holes'
3. Lighter in colour

4. Cost - Typical cost is $76/ ft2

For balau timber, it can also be used in longer lengths, such as 12 to 14 feet for a typical 20-30mm thick by 70mm width length of timber. For chengai timber, the lengths should be shorter such as 6-8 feet for a typical 20-30mm by 70mm width length of timber. This is to reduce the chance of warping, which can occur more readily under our tropical sun.

The presence of  'pin-holes' gives timber its natural look and feel. It also allows the timber to 'breathe' so to speak. However, due to weathering, there will be yellow/white sap that is produced over time. 

The sap causes chemical reactions with the paint or motar of external walls and causes weathering effects to the timber, making it look dull and old.

Some suppliers will advise that the timber (whether it is balau or chegnai) should be left in the sun to 'weather' first before installation.

Unfortunately this does not completely eliminate the problem. Hence, to further protect it, after it is cut and dried in the sun, the timber is coated with a sealant (eg: Hickson coating) that helps to seal the surface. It also gives the timber a more 'varnished' yet natural woody look.  The colour variations of the timber strips are maintained to a certain degree.

It is advised that chengai timber be used for external cladding as it is lighter and possibly more stable. There is less likelihood of warpage and the weathering effects are less severe. Balau timber, even with its hardness can crack over prolonged exposure to the weather. The cracks usually appear within the timber.

At the end of the day, the timber is a natural material. The sealant may tarnish over time, and the sap from within the timber may again surface through the pin-holes. So to maintain best quality the sealant may have to renewed every year or so.

Hence, based on the properties, chengai timber is used more often in external cladding, while balau is used for timber trellis, or timber decking to outdoor areas. At the end of the day, of course price matters. The cheaper alternative of balau may be used externally if large quantities is required for external cladding too.

An effective alternative is to use reconstituted timber. Suppliers today have a huge variety of it, and it comes in various colours and texture. It is commonly used for landscape decking, especially for condominiums as it is durable and maintains consistency over time. Recently it has been used at Sentosa for the decking. At the marine club One Degree 15, it has been even been used as wall cladding.